Police from the northwestern Mexican border city of Tijuana and army troops found a tunnel running under the U.S.-Mexican border that apparently held several tons of drugs, officials said.
Tijuana police chief Jesus Alberto Capella Ibarra and army commanders cordoned off the tunnel, which was found on Wednesday afternoon.
The tunnel could contain up to 10 tons of drugs, security officials told Efe without providing any information on arrests.
The tunnel is near the Tijuana International Airport and about 100 meters (327 feet) from the U.S. border.
Smugglers built the tunnel inside a warehouse and equipped it with rails to make it easier to move drugs.
The tunnel has a diameter of six or seven meters (19 or 23 feet) and metal stairs that lead outside.
Smugglers constructed this tunnel just a few meters from where the first tunnel between Tijuana, located in Mexico's Baja California state, and California was found in 1992.
Since the 1990s, authorities have discovered many clandestine tunnels along the border.
People traffickers and drug cartels often use clandestine tunnels to cross the vast U.S.-Mexican border, which runs 3,200 kilometers (1,988 miles). EFE